JPH0962024A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an org. photoreceptor having satisfactory sensitivity in positive electrification, less liable to the rise of residual potential due to repetitive use and excellent in durability by incorporating specified polyaniline into a surface protective layer. SOLUTION: When a photosensitive layer 2 is formed on an electrically conductive substrate 1 by successively laminating an electric charge transferring layer 2a based on an org. material and an electric charge generating layer 2b and a surface protective layer 3 is further laminated on the layer 2 to obtain an electrophotographic photoreceptor having sensitivity in positive electrification, polyaniline represented by the formula is incorporated into the protective layer 3. In the formula, (n) is a positive integer. The polyaniline has satisfactory compatibility with a resin used as a binder in general, e.g. polycarbonate, polyester, polyamide, polystyrene resin, vinyl chloride resin, vinyl acetate resin, (meth) acrylic resin, polyvinyl butyral resin, polyvinyl formal resin or polyvinyl acetal resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor for electrophotography, and more particularly, to a positively charged organic photoreceptor for electrophotography having a specific surface protective layer.

[0002]

2. Description of the Related Art Conventionally, the mainstream of electrophotographic photoconductors is an inorganic photoconductor using an inorganic photoconductive material such as selenium, selenium alloy, zinc oxide, and cadmium sulfide. However, recently, organic photoconductors using organic photoconductive materials have been actively developed and put into practical use because of advantages such as nontoxicity, film-forming property (productivity), light weight, and low price. . Among them, a so-called function-separated laminated type organic photoconductor in which the photosensitive layer is divided into a charge generation layer that receives light to generate charge carriers and a charge transport layer that moves the generated charge carriers is used. Mainstream of development because it has many advantages such as being able to significantly improve the sensitivity by forming and combining it with a material optimal for the function of the layer, and increasing its spectral sensitivity according to the wavelength of the exposure light. Since then, it has been put into practical use and is being used in electrophotographic devices such as copiers, printers and fax machines.

In the function-separated laminated organic photoreceptor,
The charge generation layer absorbs light to generate charge carriers,
It is important that the generated charge carriers move promptly and be injected into the conductive substrate or the charge transport layer without being recombined and disappeared or trapped. For this reason, it is desirable to make the charge generation layer as thin as possible, and in the currently practically used photoreceptors, the thickness of the charge generation layer is on the order of submicrons. On the other hand, the charge transport layer needs to have a certain thickness in order to exhibit the charge holding function, and has a thickness of several μm to several tens μm. In order to protect such a thin charge generating layer and make it a long-life photoreceptor, a photoreceptor currently in practical use is a photosensitive layer in which a charge generating layer and a charge transport layer are laminated in this order on a conductive substrate. It has a configuration including. In the photoconductor having such a structure, the charge transporting agent that is generally used at present is an electron-donating substance such as a pyrazoline compound, a hydrazone compound, an oxazole compound, or a carbazole compound. Therefore, it will be used with negative charging.

By the way, the photosensitive member is
Normally, it is repeatedly used in the processes of charging, image exposure, development, transfer, cleaning, and neutralization, but since charging is usually performed by corona discharge, the photoconductor is always exposed to the corona discharge atmosphere. There is a problem that it deteriorates under the influence of active gases such as ozone and NO _{x that} are generated. Therefore, the positive corona discharge is more stable than the negative corona discharge, and the ozone, NO _x
The amount of active gas generated is small, and therefore positively charged photoreceptors are less prone to deterioration, and inorganic photoreceptors such as selenium and selenium-tellurium alloys, which have been used conventionally, are positively charged. There is a strong demand for an organic photoconductor that can be used by positive charging because it can be used by charging and therefore can utilize these electrophotographic process technologies.

In order to obtain a positive charge in a structure in which a charge transport layer is laminated on an ordinary charge generating layer, an electron accepting substance such as trinitrofluorenone may be used as a charge transporting agent. Most substances are not generally used because they usually have high mobility, are chemically unstable, and are harmful. Therefore, in order to enable positive charging by using an electron donating substance, a structure in which a charge transport layer and a charge generating layer are laminated in this order on a conductive substrate is adopted.

However, in the photoconductor having such a structure, the charge injection property of the carrier from the charge generation layer to the charge transport layer is large and the chargeability is lowered, and the thin film charge generation layer serves as a surface layer, so that the mechanical strength is low. Has a small value and is inferior in durability. Therefore, a charge transport layer, a three-layer structure in which a surface protection layer is further provided on the charge generation layer, or a four-layer structure of a charge transport layer, a charge generation layer, a charge injection blocking layer, and a surface protection layer, or a charge transport layer In the two-layer structure of a charge generation layer and a charge generation layer, the resin ratio of the charge generation layer is increased to increase the film thickness to improve the mechanical strength, and the charge generation layer is added with a charge transport substance to improve the sensitivity. Have been proposed (for example, The 3rd International
al Congress in Advances i
n Non-Impact Printing Tec
Hnologies Proceedings p115; Electrophotographic Society of Japan 59th Research Symposium Proceedings p184).

As the surface protective layer of the photoreceptor having such a constitution, polyester resin, polyvinyl butyral resin,
Resin thin films such as phenol resin, cellulose acetate, styrene maleic anhydride copolymer, polyamide resin, polyimide resin, and melamine resin have been proposed (for example, Japanese Patent Publication No. 38-15446 and Japanese Patent Publication No. 51-15748).
JP-B, JP-B-60-55357, JP-B-61-
22345, etc.).

[0008]

In the case of a photoreceptor having a structure in which a charge transporting layer and a charge generating layer are laminated in this order on a conductive substrate to have sensitivity by positive charging and a resin insulating layer is used as a surface protective layer, Among the charge carriers generated in the charge generation layer, holes are injected into the charge transport layer, move inside the charge transport layer to reach the substrate, and electrons are injected into the surface protection layer and move inside the surface protection layer. It reaches the surface and the surface charge is neutralized. However, since it takes time for the electrons to move in the surface protective layer, if the thickness of the surface protective layer is large, the electrons are trapped and the residual potential rises, which also causes a large variation in characteristics during repeated use. The problem occurs. If a thin film is used in order to avoid such a problem, a problem occurs in terms of durability due to scratches, abrasion, etc. due to repeated use.

The present invention has been made in view of the above points, and provides an organic photoreceptor having positive sensitivity, good sensitivity, little increase in residual potential due to repeated use, and excellent durability. The purpose is to provide.

[0010]

According to the present invention, the above-mentioned problems include a photosensitive layer in which a charge transport layer containing an organic material as a main component and a charge generating layer are laminated in this order on a conductive substrate. In the electrophotographic photoreceptor having a surface protection layer laminated thereon and having a positively charged sensitivity, the problem can be solved by incorporating the polyaniline represented by the following general formula (I) into the surface protection layer.

[0011]

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[In the formula (I), n represents a positive integer. The structure of the polymer of the general formula (I) is already “Syn.
thetical Metals: 21 volumes, p21 (198
8) ”and the like, but it is an insoluble and infusible substance and has poor processability, and it is difficult to form a film containing this substance, and it is used for the surface protective layer of the photoconductor. Was not considered. The present inventors have found that the above-mentioned polyaniline is soluble in the solvent N-methylpyrrolidone (NMP), proceeded with the investigation, and completed the present invention.

The polyaniline according to the present invention is a resin generally used as a binder, such as polycarbonate, polyester, polyamide, polystyrene resin, vinyl chloride resin, vinyl acetate resin, (meth) acrylic resin, Shows good compatibility with resins such as polyvinyl butyral resin, polyvinyl formal resin, and polyvinyl acetal resin. This polyaniline is NM
A solution prepared by dissolving P in PMP or a solution prepared by dissolving this polyaniline in NMP together with the binder as described above,
By forming the surface protective layer as a coating liquid, a photosensitive member having sensitivity with positive charging, little increase in residual potential due to repeated use, and excellent abrasion resistance and durability can be obtained. When polyaniline is used as a mixture with a binder, it is effective only to include a very small amount of polyaniline, for example, several% by weight.

Further, by doping the polyaniline represented by the general formula (I) with a protonic acid, a composition having improved solvent solubility and conductivity can be obtained. It is more preferable to use such a composition instead of polyaniline. As the protonic acid to be doped, organic acids such as sulfonic acid, carboxylic acid, phosphoric acid or latent acids are preferably used.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polyaniline represented by the above-mentioned general formula (I) according to the present invention is "Journal".
of the Chemical Society: C
chemical Communication, p. 17
36 (1989) ”, that is, by oxidatively polymerizing an aqueous solution of aniline and sulfuric acid at low temperature using ammonium peroxodisulfate as an oxidant, and neutralizing and dedoping the resulting precipitate powder with aqueous ammonia. It is a solvent-soluble polyaniline that is soluble in NMP. Further, the composition obtained by doping such a polyaniline with a protonic acid has a higher solvent solubility.

The thickness of the surface protective layer containing polyaniline according to the present invention is preferably 0.1 μm to 20 μm, and more preferably 5 μm to 15 μm. When the surface protective layer is formed of polyaniline and a binder, the polyaniline content is effective even if the amount is very small, but is preferably 5% by weight or more. In order to fully express the function of the surface protective layer, to dope the polyaniline with a protonic acid,
Dip the formed surface protection layer in a solution of protonic acid, or
Alternatively, 1% by weight to 200% by weight, preferably 5% by weight to 150% by weight, of protic acid is added to the coating solution for the surface protective layer, and this coating solution may be used.
By adopting such a method, polyaniline becomes a composition doped with a protonic acid. As the protic acid, organic acids such as sulfonic acid, carboxylic acid and phosphoric acid, or latent acids are preferable.

The photoreceptor according to the present invention is a function-separated laminated photoreceptor in which a charge transport layer and a charge generating layer are laminated in this order on a conductive substrate, and the surface protective layer as described above is provided thereon. Is. For the charge transport layer, a solution of a polymer compound such as poly (N-vinylcarbazole), poly (vinylanthracene), and polysilane is applied on a conductive substrate and dried, or a hydrazone compound, a pyrazoline compound,
Film formation by coating and drying a coating solution of low molecular weight compounds such as enamine compounds, styryl compounds, arylmethane compounds, arylamine compounds, butadiene compounds and azine compounds dissolved in an organic solvent together with a binder having an appropriate film forming property. To be done. Binders used with these low molecular weight compounds include polycarbonate resins, polyester resins, polystyrene resins, (meth)
An acrylic resin, a silicone resin, etc. are mentioned, and are used in a ratio of 50 parts by weight to 200 parts by weight with respect to 100 parts by weight of the low molecular weight compound. The thickness of the charge transport layer is 10 μm
30 μm is desirable.

The charge generation layer is a coating solution in which the charge generation substance is dispersed alone in an organic solvent on the charge transport layer, or
It is formed by coating and drying a coating liquid that is dispersed and dissolved in an organic solvent together with a binder. Further, the thermally stable charge generating substance may be sublimed in vacuum to form a film. Examples of charge generating substances include azo pigments, anthraquinone pigments, polycyclic quinone pigments, indigo pigments, diphenylmethane pigments, azine pigments, cyanine pigments, perylene pigments, squarylium pigments, phthalocyanine pigments, etc. Is mentioned. As the binder, polyamide resin, silicone resin, polyester resin, polycarbonate resin, phenoxy resin, polystyrene resin, polyvinyl butyral resin, polyvinyl formal resin,
Polyvinyl acetal resin, (meth) acrylic resin, vinyl chloride resin, etc. may be used alone or in combination. These binders are used in an amount of 5 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 100 parts by weight of the charge generating substance. The thickness of the charge generation layer is preferably 0.05 μm to 2.0 μm.

[0019]

EXAMPLES Examples of synthesizing polyaniline according to the present invention and specific examples of the present invention will be described below, but it goes without saying that the present invention is not limited thereto. In the following, "parts" means "parts by weight". Synthesis example of polyaniline 98 parts of sulfuric acid and 93 parts of aniline are added to 1000 parts of distilled water, water-cooled to -5 ° C. A solution prepared by adding 196 parts of sulfuric acid and 196 parts of ammonium peroxodisulfate to 1000 parts of distilled water was added to this cooling liquid at -5 ° C.
Under stirring, the solution is gradually added with stirring. After the addition, if left to stand overnight in the cooled state, a deep blue-green precipitate is formed. The precipitate is washed with distilled water and then with aqueous ammonia until the presence of sulfate is no longer recognized. Further, when washed with distilled water and dried, a deep blue polyaniline is obtained. The polyaniline thus obtained was satisfactorily dissolved in the solvent N-methylpyrrolidone (NMP) up to 8% by weight, and a blue solution was obtained. LiBr was dissolved in NMP at a concentration of 0.01 mol / dm ^3. Gel permeation chromatography (GP
When the molecular weight was measured by C), the weight average molecular weight M
_W was 150,000 (polystyrene conversion).

Next, examples will be described. FIG. 1 is a schematic cross-sectional view of a photosensitive member according to an embodiment of the present invention. A photosensitive layer 2 in which a charge transport layer 2a and a charge generating layer 2b are laminated in this order is provided on a conductive substrate 1, and a photosensitive layer 2 is provided thereon. A surface protective layer 3 is provided. Example 1 outside diameter 60 mm, inner diameter 56 mm, length 298 mm, the outer peripheral surface roughness cylindrical conductive substrate 1 of the outer peripheral surface on consisting of 1.0μm of aluminum alloy with a maximum height R _{ma x,} the charge transport material 10 parts of a hydrazone compound represented by the following structural formula (II) -1 and polycarbonate (manufactured by Mitsubishi Gas Chemical Co., Inc .; trade name "UPILON PCZ-300") 10
Part and 80 parts of tetrahydrofuran were applied by dip coating to form a charge transport layer 2a having a dry thickness of 20 μm.

[0021]

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In addition, 2.1 parts of an azo compound represented by the following structural formula (III) -1 as a charge generating substance, polyvinyl acetal (manufactured by Sekisui Chemical Co., Ltd .; trade name "S-Rex KS-1") ) 1.0 part methanol 16 parts,
A photosensitive layer 2 was formed by dispersing 4 parts of methyl ethyl ketone, further adding 60 parts of methanol and 20 parts of normal butanol, and dip-coating a coating solution to form a charge generation layer 2b having a dry thickness of 0.2 μm.

[0023]

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Furthermore, a coating solution prepared by adding 10% by weight of camphorsulfonic acid to polyaniline to a solution prepared by dissolving the polyaniline obtained in the above-mentioned Synthesis Example in NMP at a concentration of 8% by weight. By dip coating, a surface protective layer 3 having a dry thickness of 5.0 μm was formed to prepare a photoreceptor. Example 2 In Example 1, the charge transport material was replaced by the following structural formula (II).
A photosensitive layer was formed in the same manner as in Example 1 except that the charge generating substance was replaced with an azo compound represented by the following structural formula (III) -2 in place of the hydrazone compound represented by -2.

[0025]

Embedded image

On this photosensitive layer, the coating solution for the surface protective layer of Example 1 was further added with a polycarbonate having twice the weight of polyaniline (manufactured by Mitsubishi Gas Chemical Co., Inc .; trade name "UPILON PCZ-300"). Was added and dissolved to prepare a coating solution by dip coating, and a surface protective layer having a dry thickness of 5.0 μm was formed to prepare a photoreceptor. Example 3 In Example 1, the charge transport material was replaced by the following structural formula (II).
A photosensitive layer was formed in the same manner as in Example 1 except that the charge generating substance was replaced with the compound represented by the following structural formula (III) -3 in place of the compound represented by the formula-3.

[0027]

[Chemical 6]

On this photosensitive layer, a solution prepared by dissolving the polyaniline obtained as in the above-mentioned Synthesis Example in NMP at a concentration of 8% by weight was added with a polycarbonate having a weight three times that of polyaniline (Mitsubishi Gas Chemical Co., Ltd.). (Manufactured by the trade name "UPILON PCZ-300"), and dissolved, and further 20% by weight of bis (2-ethylhexyl) based on polyaniline.
A coating solution prepared by adding hydrogen phosphate was applied by dip coating to form a surface protective layer having a dry thickness of 5.0 μm to prepare a photoreceptor.

Comparative Example 1 In Example 1, the coating solution for the surface protective layer was a copolymerized polyamide resin (manufactured by Toray Industries, Inc .; trade name “Amilan CM-80”).
00 ") and 5 parts of methanol and 100 parts of methanol, and a photoconductor was prepared in the same manner as in Example 1 except that a coating solution containing no polyaniline was used.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 1 except that the surface protective layer was not provided. Comparative Example 3 A photoconductor was prepared in the same manner as in Example 1 except that sulfuric acid was used instead of the protonic acid added to the surface protective layer coating solution.

With respect to each of the photoconductors manufactured as described above, the photoconductor characteristics were evaluated by a photoconductor process tester. The photoconductor is attached to a tester, charged at +600 V with a corotron while rotating at a peripheral speed of 60 mm / sec, and the potential at the time of no light irradiation is defined as the dark part potential V _D. After that, the potential when left in the dark for 5 seconds was measured, and the potential holding ratio V during that period was measured.
_{Calculate K5} (%). Subsequently, a halogen lamp light having an illuminance of 30 lux on the surface of the photoconductor is irradiated and the potential after 0.2 seconds is set to the bright portion potential V _L. Furthermore, the residual potential V _R with a potential after irradiation 1.5 seconds. The process of charging and exposing as one cycle as described above was repeated 10,000 times, and the characteristics of the photoconductor were measured at the initial (first) and after repeating 10,000 times. Table 1 shows the results.

[0032]

[Table 1]

As shown in Table 1, the photoreceptor of Example 1 provided with a surface protective layer made of a composition obtained by doping polyaniline with camphorsulfonic acid, a composition obtained by doping polyaniline with camphorsulfonic acid and a binder. The photoreceptor of Example 2 provided with a surface protective layer made of polycarbonate, Example 3 provided with a surface protective layer made of a composition obtained by doping polyaniline with bis (2-ethylhexyl) hydrogen phosphate and polycarbonate serving as a binder. Each of the photoreceptors of Comparative Example 1 is a photoreceptor of Comparative Example 1 that is provided with a surface protective layer made of a copolyamide resin and does not contain polyaniline, a photoreceptor of Comparative Example 2 that is not provided with a surface protective layer, and contains polyaniline as a surface protective layer. Of Comparative Example 3 wherein the composition contains a composition doped with inorganic sulfuric acid Initial charge potential is high potential holding rate than the also good residual potential is low, and repeated charge problem is less potential retention rate at the time of use even less increase in residual potential does not decrease.

[0034]

According to the present invention, a photosensitive layer is formed by laminating a charge transport layer containing an organic material as a main component and a charge generating layer in this order on a conductive substrate, and further a surface protective layer thereon. In a positive charging type electrophotographic photoreceptor formed by stacking
The polyaniline represented by the general formula (I) is contained in the surface protective layer. Alternatively, a composition obtained by doping the polyaniline represented by the general formula (I) with a protic acid is contained. By providing such a surface protective layer, it is possible to obtain an electrophotographic photoreceptor having positive sensitivity, good sensitivity, little change in characteristics due to repeated use, and excellent abrasion resistance and durability.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an embodiment of a photoconductor according to the present invention.

[Explanation of symbols]

 1 Conductive Substrate 2 Photosensitive Layer 2a Charge Transport Layer 2b Charge Generation Layer 3 Surface Protection Layer

Claims (3)

[Claims] 1. A photosensitive layer comprising a charge transport layer containing an organic material as a main component and a charge generating layer laminated in this order on a conductive substrate, and a surface protective layer further laminated thereon. An electrophotographic photoreceptor having a positive charge and sensitivity, wherein the surface protective layer contains polyaniline represented by the following general formula (I). Embedded image [In formula (I), n represents a positive integer. ] 2. A photosensitive layer comprising a charge transport layer containing an organic material as a main component and a charge generating layer laminated in this order on a conductive substrate, and a surface protective layer further laminated thereon. An electrophotographic photosensitive member having a positive charge and sensitivity, wherein the surface protective layer contains a composition obtained by doping the polyaniline represented by the general formula (I) with a protonic acid. Photoconductor. 3. A protonic acid is sulfonic acid, carboxylic acid,
The electrophotographic photoreceptor according to claim 2, which is an organic acid such as phosphoric acid or a latent acid.